A weep or a weep-brick is a small opening that allows water to drain from within an assembly. Weeps are located at the bottom of the object to allow for drainage; the weep hole must be sized adequately to overcome surface tension

Surface tension

Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...

.

In building construction, weeps are typically found in a masonry cavity wall

Masonry Veneer

Masonry veneer walls consist of a single non-structural external layer of masonry work, typically brick, backed by an air space. The innermost element is usually structural, and may consist of wood or metal framing or masonry...

, just above the flashing

Flashing (weatherproofing)

Flashing refers to thin continuous pieces of sheet metal or other impervious material installed to prevent the passage of water into a structure from an angle or joint...

. Weeps may take several forms, including:

• Open head joints (the vertical joints between brick
  Brick
  A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
  
  s)
• Cotton rope wicking
• Formed plastic or metal tubes, which may include insect screening.

Weeps may also be necessary in a retaining wall

Retaining wall

Retaining walls are built in order to hold back earth which would otherwise move downwards. Their purpose is to stabilize slopes and provide useful areas at different elevations, e.g...

, so water can escape from the retained earth, thus lessening the hydrostatic load on the wall and preventing moisture damage from freeze/thaw cycles. In such cases the weeps consist of small-diameter plastic, clay or metal pipes extending through the wall to a layer of porous backfill.

Typically, weeps are arranged to direct water which may have entered an assembly from outside back to the outside. Weeps may also be found in metal window

Window

A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...

s and glazed curtain wall

Curtain wall

A curtain wall is an outer covering of a building in which the outer walls are non-structural, but merely keep out the weather. As the curtain wall is non-structural it can be made of a lightweight material reducing construction costs. When glass is used as the curtain wall, a great advantage is...

s to permit internal condensation

Condensation

Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

to escape.